Twitter's Lord did not specify the method by which hackers
penetrated its system. However, he mentioned vulnerabilities
related to Java in Apple's Safari Web browser and Mozilla's
Firefox browser, and noted an advisory from the U.S. Department
of Homeland Security that users disable Java on their
computers.

There are also suggestions in Lord's post that the hacking
attempt was organized, and possibly linked to recent cyberattacks
on other media institutions like the Wall Street Journal and the
New York Times. Lord wrote:

This attack was not the work of amateurs, and we do not believe
it was an isolated incident. The attackers were extremely
sophisticated, and we believe other companies and organizations
have also been recently similarly attacked. For that reason we
felt that it was important to publicize this attack while we
still gather information, and we are helping government and
federal law enforcement in their effort to find and prosecute
these attackers to make the Internet safer for all users.